Osteoarthritis (OA) is a degenerative disease of cartilage and is associated with severe pain and immobilization. Early detection of OA is necessary for efficient therapeutic intervention. In the early stage of OA, there is a loss of proteoglycan (PG) molecules from articular cartilage. Recently, we have shown the feasibility of indirectly measuring PG loss in cartilage by quantitation of sodium by 23Na MRI of articular cartilage in-vivo and in-vitro. An accurate quantitation must account for both the intra-cartilage sodium, which is of interest, and the extra-cartilage synovial fluid. To determine the relative contributions of these two sources of 23Na MRI signal, we performed T1 and T2 weighted 23Na MRI of patella specimen placed in a bath of physiologic concentration saline. Preliminary results indicate that it is possible to remove the contribution from synovial fluid by judicious selection of imaging parameters. Further quantitation in vitro and in vivo is in progress.